Secondary cells which can be charged and discharged repeatedly are used extensively.
Meanwhile, solar cells which use the photovoltaic effect produced by a semiconductor substrate of silicon, for example, have been used very often as a photoelectric transducer that converts optical energy into electric power. Also well known are solar secondary cells in each of which a secondary cell that not only stores the output power of a solar cell but also releases the stored power and supplies it to various kinds of loads in order to use the output of the solar cell effectively and the solar cell are combined. Such a solar secondary cell is disclosed in Patent Document No. 1, for example.
To produce the photoelectric conversion as efficiently as possible, a solar cell is generally formed in the shape of a thin film. When a compact solar secondary cell is formed by combining such a solar cell and a secondary cell together, the secondary cell is arranged on the back surface opposite from the light incident side. As disclosed in Patent Document No. 1, the secondary cell is formed by stacking a positive electrode (cathode) layer, an electrolytic layer and a negative electrode (anode) layer in this order on the back surface of the solar cell.
Patent Document No. 2 discloses a solar cell.